1. Field of the Invention
The present invention relates to a signal conversion device, and more particularly to a wireless RF signal conversion device. The present invention relates to a radio frequency tag and the method for operating the same, and more particularly to a radio-frequency tag having the information for comparing digital logic and the method for operating the same.
2. Description of Related Art
The Radio-Frequency Identification (RFID) system has been recognized as a major development trend in the electronic industry, and the system is designed based on different modulation methods such as OOK (100% ASK), x % ASK, FSK, PSK and FHSS as required, thereby achieving different signal transmission formats.
In particular, BPSK is a signal modulation mode that has an uninterrupted transmission capacity, a high data rate, and a noise immunity property; therefore it has been widely used in various techniques involving wireless signal transmission. However, BPSK signal format is more complex, thus it is more complicated to decode the BPSK signal to obtain the baseband digital information contained therein.
Hence, BPSK signal reading device usually requires a microprocessor to demodulate the signal. However, to a simple passive RFID tag circuit that is unable to use the microprocessor for demodulation, a low-cost and power-saving BPSK signal conversion device must be designed to extract the baseband digital information contained in the BPSK signal.
Referring to FIG. 1, a block diagram of a conventional BPSK demodulation structure is shown. As illustrated in the diagram, the general demodulation structure is realized using digital circuits, which has the advantages of lower power dissipation and easier circuit design compared to the structure based on the conventional Costas loop.
The concept of the demodulation structure design is based on the XOR gate, which replaces the product detector of the conventional Costas loop and a feedback modulator is used to replace the function of the original phase detector, so as to lower the circuit complexity.
However, the problem of demodulation error often occurs in such circuit structure, a data decoder must be used to compensate the demodulation signal, or even worse, a microprocessor is sometimes needed to perform the signal compensation algorithm. Therefore, such a circuit structure may have the advantage of circumventing analog components but it increases the design complexity.
In addition, lowering the manufacturing cost of the passive RFID tag to the level appropriate for mass production is an issue worth discussing in the event that the wireless RFID system is promoted such that it replaces the current bar code system for use in the inventory tracking or product identification management systems.
For instance, considering the conventional RFID tag reading method shown in FIG. 2, the method adopts a scanning-based pre-processing structure to achieve lower probability of tag collisions.
The core of the design involves issuing an inquiry signal to the RFID tag by the tag reader prior to authentication. Subsequently, the RFID tag sends its ID back to the tag reader. The tag reader, after receiving the ID of the RFID tag, analyzes the ID and the positions where collisions occur. Finally, the positions where collisions occur will be sent back and saved in the memory of the RFID tag. Thereafter, ID authentication is carried out based on uncollided bits.
The RFID tag system designed based on the aforementioned design core solves the bit collision problem and lowers the communication time, however, the collision information sent back by the tag reader is required to be saved in the RFID tag, therefore a storage device for storing information must be designed into the RFID tag. Sometimes, a microprocessor must be used to run the algorithm, and thus the manufacturing cost is increased, which impedes the progress of replacing the current bar code ID management system.
In summary, it has become a critical issue to designers of the RFID tag to propose a low-cost BPSK signal conversion device that dissipates low power to extract the baseband digital information contained in the BPSK signal, as well as a simple, correct and fast passive wireless RFID tag and the method for operating the same so as to circumvent the tag collision problem and lower the RFID tag manufacturing cost.